[Usenet: very common] Abbreviation: You Have Been Trolled (see
troll, sense 1). Especially used in “YHBT.
YHL. HAND.”, which is widely understood to expand to “You
Have Been Trolled. You Have Lost. Have A Nice Day”. You are quite
likely to see this if you respond incautiously to a flame-provoking post
that was obviously floated as sucker bait.